1. Field of the Invention
The invention relates to a fuel injection nozzle for self-igniting internal combustion engines.
2. Description of the Prior Art
Fuel injection nozzles of this type with which this invention is concerned are known, for instance, from German Patent DE 43 03 813 C1 and from the published book entitled Bosch Kraftfahrtechnisches Taschenbuch [Bosch Automotive Handbook], 22nd Edition, 1995, pages 526 ff.
In such fuel injection nozzles, the injection ports are embodied cylindrically. The conversion of the fuel pressure into a speed of the injected fuel stream is done inside a small region, which results in great losses of efficiency.
According to the present invention a fuel injection nozzle of this type provides an increase in efficiency in the conversion of the fuel pressure into a speed of the fuel stream fed in, and as a result the efficiency of fuel distribution in the engine, are increased. The fuel injection nozzle is also intended to reduce NOx in particulate values.
Because the injection port cross section toward the combustion chamber of the engine, after initially narrowing, widens again, an optimal conversion of the pressure into a speed of the fuel stream and thus high efficiency of fuel distribution in the internal combustion engine is attained in an especially simple way. While specifically in the convergent region of the fuel injection nozzle higher speeds are generated, while in its divergent portion it is possible to generate a spray with small particles. Thus a shift in the region of maximum distribution away from the fuel injection nozzle because of higher speeds of the fuel stream that emerges from the fuel injection nozzle known from the prior art is advantageously counteracted by the divergent portion of the fuel injection nozzle. As a result of an optimal conversion of the pressure of the fuel stream into its speed, the tendency to cavitation is thus also reduced. The smallest injection port cross section advantageously extends in the axially middle region of the injection port opening, so that the divergent and the convergent injection port regions each have about the same axial length.
Furthermore, such a fuel injection nozzle can be produced especially economically, for instance by spark erosion.
With respect to the embodiment of the injection ports, the most various forms are possible. Advantageously, the injection ports have one of the following cross-sectional shapes: a circular form, an elliptical form, or slitlike form.